The degradation of diamond limits its use as filler in hardmetals (e.g., cemented carbide and cermets). The degradation occurs during fabrication and use. Forms of diamond degradation include reversion to graphite, oxidation, dissolution, cracking and reaction. Diamond""s Knoop 100 hardness is 75-100 gigapascal (GPa) and greater. The next hardest known substance cubic boron nitride has a Knoop 100 hardness of about 45 GPa. Both are called superhard materials. Engineer and scientists have endeavored to incorporate this hardest known substance in materials but diamond""s degradation persists.
Diamonds in materials made using hot-press matrix powders dissolve in base metals, react with the base metal to from carbides, oxidize, and degrade to graphite. Hot-press matrix powders are designed to be mixed with synthetic diamonds to make tools for sawing, drilling, grinding and honing materials such as stone, rock, green concrete, concrete, reinforced concrete, asphalt, refractories, and glass. Hot-press matrix powders include at least tungsten metals or various tungsten carbide species and a base metal. Base metals include metals and their alloys such as cobalt, tungsten, iron, nickel, and copper. The solubility of carbon in cobalt, nickel, and iron; the existence of carbides of cobalt, tungsten, and iron; and the oxygen in copper provide explanations for the observed degradation of diamond in materials made using hot-press matrix powders.
Diamonds surface set on or mixed in materials made using infiltration alloys dissolve, oxidize, crack, and degrade to graphite. Infiltration alloys are designed to wet powders of at least tungsten metals or various tungsten carbide species including synthetic diamonds either surface set or intimately mixed in to make tools such as bits, core bits, drill bits, and polycrystalline bit bodies, for dressing, sawing, and drilling, grinding. Infiltration alloys include a major constituent such as copper, nickel, zinc, manganese, and cobalt with small amounts of one or two other elements such as iron, molybdenum, silicon, silver, lead and perhaps lead. The solubility of carbon in cobalt, nickel, and iron; the existence of carbides of cobalt, tungsten, silicon, molybdenum and iron; the swelling and shrinking during eta reaction to precrack diamond and the oxygen in copper provide explanations for the observed degradation of diamond in materials made using infiltration alloys.
Diamonds in materials (sintered polycrystalline diamond) made using liquid-phase sintering oxidize, crack, and degrade to graphite. Sintered polycrystalline diamond, in addition to containing about 5 to 10 volume percent of a metal phase such as cobalt, nickel and iron, may include graphite and are used in tools in the metalworking, mining and construction. Ironically, the cobalt, nickel and iron that catalyze the high-pressure high-temperature conversion of graphite to diamond, catalyze the reversion of diamond to graphite at about 700xc2x0 C. at about atmospheric pressure. Sintered polycrystalline diamond bodies are size limited by heating pressurizing equipment.
It is apparent that there is a need for a superhard hardmetal (a hardmetal including a superhard material such as a diamond filler, a boron nitride filler, a carbon boron nitride and combinations thereof). Also, it is apparent that there is a need for a method for making a superhard filler hardmetal. There is also a need for superhard filler hardmetal having sizes and shapes unattainable by the high-pressure high-temperature process.
The present invention satisfies the need for a superhard filler hardmetal (e.g., cermet or cemented carbide). Also, the present invention satisfies the need for a method for making a superhard filler hardmetal. The present invention also satisfies the need for a superhard filler hardmetal having sizes and shapes unattainable by the high-pressure high-temperature process.
In an embodiment of the present invention, a binder metal or matrix embeds a single crystal and/or polycrystalline superhard filler to create superhard filler hardmetal hating substantially little to no porosity, preferably, a porosity rating of substantially A06, B00, C08 or better, more preferably A02, B00 and C00 or better, and most preferably A00, B00 and C00. The superhard filler may make-up about 1 vol. % to about 80 volume percent (vol. %) and have a grain size of about submicron to about 1500 micrometers Preferred superhard filler included diamond, boron nitride and carbon nitride. In addition to the superhard filler, the superhard filler hardmetal may include at least one first hard component of, for example, carbides, nitrides, borides, oxides, intermetallics, mixtures thereof, solid solutions thereof, and combinations thereof. Also in addition to the first hard component the superhard filler hardmetal may include additional hard components of, for example carbides, nitrides, borides, oxides, intermetallics, mixtures thereof, solid solutions thereof, and combinations thereof. The size or size distribution of the first hard component, the second hard component, . . . etc., and the superhard filler may each be unique and different, however, size or size distribution are preferably substantially the same. The superhard filler hardmetal may be incorporated into, for example, at least a portion of an oil field tool (e.g., a button), a petroleum industry or exploration tool (e.g., a button or portion of a button), a mining tool (e.g., a hard tip or portion of a hard tip), a construction tool (e.g., a hard tip or portion of a hard tip), and a material removal tool (e.g., a metal or nonmetal cutting insert or portion of an insert).
In an embodiment of the present invention, a coating is provide to superhard filler prior to incorporating it into the superhard filler hardmetal. The coating may have thickness up to about 2.0 xcexcm or more. The coating has the same or different composition as the embedding binder metal or matrix. The coating may include one or more layers.
In another embodiment of the present invention, a superhard filler hardmetal is formed by consolidating a shaped green body of a mixture of a superhard filler and a binder metal or matrix precursor at a preselected temperature, superatmospheric pressure and time at temperature, the time and temperature at superatmospheric pressure being sufficient to form the superhard filler hardmetal without the forming a liquid.
In a preferred method, a consolidation method such as rapid omnidirectional compaction (ROC) is used. In this manner, the time at superatmospheric pressure is less than the time at temperature. For example, the time at superatmospheric pressure may be about 2 seconds to about 10 minutes, preferably, about 2 seconds to about 1 minute and the time at temperature may be about 10 minutes to about 6 hours, preferably, about 15 minutes to about 1 hour. The superatmospheric pressure may be at least about 10,000 pounds per square inch (psi) and at most about 1,000,000 psi.